use multiple runners for the multi-arch build

.gitea/workflows/ci.yml

@@ -63,21 +63,77 @@ jobs:
           token: ${{ secrets.CODECOV_TOKEN }}
   build:
     name: Build and push image
-    runs-on: ${{ matrix.runner }}
+    runs-on: ${{ matrix.arch.runner }}
     strategy:
       matrix:
-        runner: [ubuntu-latest, ubuntu-arm-latest]
+        arch:
+          - runner: ubuntu-latest
+            platform: linux/amd64
+          - runner: ubuntu-arm-latest
+            platform: linux/arm64
     permissions:
       packages: write
     needs: tests
     steps:
       - uses: actions/checkout@v4
-      - name: Login to the Container Registry
+      - name: Prepare
+        run: |
+          platform=${{ matrix.arch.platform }}
+          echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV
+      - name: Generate metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+      - name: Login to the container registry
         uses: docker/login-action@v3
         with:
           registry: brosner.dev
           username: brosner
           password: ${{ secrets.CI_TOKEN }}
+      - name: Setup docker buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Build image
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          labels: ${{ steps.meta.outputs.labels }}
+          annotations: ${{ steps.meta.outputs.annotations }}
+          target: prod
+          platforms: ${{ matrix.arch.platform }}
+          outputs: type=image,push-by-digest=true,name-canonical=true,push=true
+      - name: Export digest
+        run: |
+          mkdir -p ${{ runner.temp }}/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "${{ runner.temp }}/digests/${digest#sha256:}"
+      - name: Upload digest
+        uses: actions/upload-artifact@v4
+        with:
+          name: digests-${{ env.PLATFORM_PAIR }}
+          path: ${{ runner.temp }}/digests/*
+          if-no-files-found: error
+          retention-days: 1
+  merge:
+    runs-on: ubuntu-latest
+    needs:
+      - build
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: ${{ runner.temp }}/digests
+          pattern: digests-*
+          merge-multiple: true
+      - name: Login to the container registry
+        uses: docker/login-action@v3
+        with:
+          registry: brosner.dev
+          username: brosner
+          password: ${{ secrets.CI_TOKEN }}
+      - name: Setup docker buildx
+        uses: docker/setup-buildx-action@v3
       - name: Generate metadata
         id: meta
         uses: docker/metadata-action@v5
@@ -87,22 +143,11 @@ jobs:
             type=ref,event=branch
             type=ref,event=pr
             type=sha
-          labels: |
-            org.opencontainers.image.title=teufa
-            org.opencontainers.image.description=teufa container image
-            org.opencontainers.image.source=https://brosner.dev/brosner/teufa
-            org.opencontainers.image.licenses=MIT
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
-      - name: Setup docker buildx
-        uses: docker/setup-buildx-action@v3
-      - name: Build image
-        uses: docker/build-push-action@v6
-        if: gitea.ref == 'refs/heads/main'
-        with:
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-          annotations: ${{ steps.meta.outputs.annotations }}
-          target: prod
-          platforms: ${{ matrix.runner == 'ubuntu-latest' && 'linux/amd64' || 'linux/arm64' }}
-          push: true
+      - name: Create manifest list and push
+        working-directory: ${{ runner.temp }}/digests
+        run: |
+          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf '${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@sha256:%s ' *)
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.version }}